Three-ski device



FIG. 1 illustrates a front left plan view of an ornamental design of the three-ski device in accordance with the present invention;

FIG. 2 illustrates a rear left plan view of the invention of FIG. 1;

FIG. 3 illustrates a bottom elevational view of the invention of FIG. 1;

FIG. 4 illustrates a top elevational view of the invention of FIG. 1; and,

FIG. 5 illustrates a side elevational view of the invention of FIG. 1.

The broken line showing of a seat is for illustrative purposes only and forms no part of the claimed design. 

I claim an ornamental design of a three-ski device, as shown and described. 